Liquid crystal display (LCD) is referred to as LCD panel, which has many advantages, such as thin body, energy saving, no radiation. It has been widely used, such as LCD TV, smart phone, digital camera, tablet PC, computer screen, or laptop screen, etc., and dominates the field of flat panel displays.
The structure of the liquid crystal panel is usually composed of a color filter (CF) substrate, a thin film transistor array substrate (TFT substrate), and a liquid crystal layer (Liquid Crystal Layer), which controls the rotation of the liquid crystal molecules in the liquid crystal layer by applying a driving voltage to the two glass substrates, and refracts the light of the backlight module to generate a picture.
For the traditional liquid crystal panel, a plurality of color resists for filtering and a black matrix (BM) for light shielding are arranged on the side of the CF substrate, and a special Photo Space (PS) is disposed between TFT substrate and CF substrate to support the cell thickness of the liquid crystal layer. With the development of display technology, there has been a technology that combines BM and PS (Black Photo Spacer, BPS).
BPS 1 tone technology is one of the most cost-effective BPS technology. BPS 1 tone technology is a process technology that the mask used in the BPS process has only one transmittance and only one intensity of light perceived by the corresponding BPS material. However, the conventional BPS 1 tone technology requires the use of organic planarization (PFA) Layer because the conventional BPS 1 tone technology uses an Island structure, which uses two color blocks stacked to act as a main photoresist spacer (Main PS) and a color block to act as a secondary photoresist spacer (Sub PS). Since the difference of the height between the two color blocks and one color block is too large, the difference between the height of the main photoresist spacer and the secondary photoresist spacer will be too large. It needs the organic planarization layer pair to flatten the height of the two-layer color resist.
In order to save the costs, eliminating the organic planarization layer of BPS TFT substrate was developed. Referring to FIG. 1 and FIG. 2, the TFT substrate which is omitted with the organic planarization layer use the single-layer of the first island-shaped color resist block 402 to pad the main photoresist spacer 701. It also uses the single-layer of the second island-shaped color resist block 403 to pad the sub-photoresist spacer 701. The second island-shaped color resist block 403 with the sub-photoresist spacer padded up is gray-scale exposed with a slit diffraction type (SLT) mask so that the secondary Shining at the island-shaped color resist block 403 is semi-translucent; The difference between the corresponding main photoresist spacer 701 and the sub-photoresist spacer 702 is the height h1 of the first island-shaped color resist block 402 and the height h2 of the second island-shaped color resist 403. The organic planarization layer may not be used on the color resist layer 401, the first island-shaped color resist block 402 and the second island-shaped color resist block 403, but silicon nitride (SiNx) and the second passivation layer PV2 combined with silicon oxide (SiOx) covers the color resist layer 401, the first island-shaped color resist 402, the second island-shaped color resist 403, and the existing first passivation layer PV1. When manufacturing the BPS TFT substrate, a TFT T and a first passivation layer PV1 covering the TFT T are first formed on the base substrate 10. Then, a color resist is deposited and patterned to form a color resist layer 401, the first island-shaped color resist block 402 and a second island-shaped color resist block 403. Then, depositing a second passivation layer PV2 and performing patterning and depositing a conductive film and etching to form a pixel electrode 601 and a common electrode 602. Finally, the second passivation layer PV2, the pixel electrode 601 and the common electrode 602 to form the integrated main photoresist spacer 701, the sub-photoresist spacer 702 and the black matrix 703.
To refer FIG. 3 and FIG. 4, there is a problem in the BPS type TFT substrate of this new architecture. Since the color resistance in the area where the black matrix 703 is located is dug, the color resist edge forms a slope. If the slope of the slope is too steep. So the second passivation layer PV2 is completed and the conductive film is further formed, the existence of the ramp causes the conductive film to be etched to be unclean and leave a residue. The remaining conductive film causes the pixel electrode 601 and the common electrode 602 to be short-circuited.